What was found
(CAN) DURING A TEST FLIGHT, AFTER THE ENGINE WAS REPAIRED FOR COMPRESSOR STALLS, WE EXPERIENCED ONE MINOR STALL. WE THEN BEGAN TO RETURN TO BASE WHEN THE ENGINE EXPERIENCED A SERIES OF RAPID STALLS, THE TOT INCREASED OVER 900 DEGREES, ENGINE POWER WAS DEGRADING/LOST, AUTOROTATION WAS ENTERED AND THE ACFT WAS LANDED ON THE MOUNTAIN TOP. THE FUEL VALVE WAS SHUTOFF UPON LANDING. NO DAMAGE OCCURED TO THE AIRFRAME. THE ENGINE MODULES, COMPRESSOR AND TURBINE WERE REPLACED ON THE MOUNTAIN TOP, AND THE APPROPRIATE MX ACTIONS WERE TAKEN. THE COMPRESSOR AND TURBINE ASSY WERE SENT FOR INVESTIGATION.